Artery of Percheron infarction: a rare cause of somnolence in a patient with sepsis and atrial fibrillation.

Artery of Percheron (AOP) occlusion is a rare cause of ischemic stroke characterized by bilateral para-median thalamic infarcts. It usually presents with altered mental status, hyper-somnolence and ocular movement disorders. Here, we report a case of cardio-embolic AOP infarction in a 72-year-old man with sepsis and new-onset atrial fibrillation. Early diagnosis is challenging, but diffuse-weighted magnetic resonance imaging demonstrates the lesion in the acute setting. Anticoagulation therapy was started and patient's mental status gradually improved.

A 72-year-old man with hypertension, hyperlipidemia, type two diabetes and peripheral vascular disease presented with sepsis from left fourth digit wet gangrene. He was started on broad spectrum antibiotics. Next morning, he was found unresponsive. Upon examination, he was deeply somnolent, pupils were equal and reactive, vertical gaze palsy was detected. No focal neurological signs were appreciated. He promptly required endotracheal mechanical ventilation because of apnea. An electrocardiogram showed atrial fibrillation (AF). Based on ophthalmologic signs, a magnetic resonance imaging (MRI) of the brain was obtained which revealed acute ischemic infarcts in bilateral thalami and posterior right temporal lobe. Diffusion-weight images (DWI) showed multiple foci of restricted diffusion with largest in the left and anterior right thalamus consistent with artery of Percheron (AOP) territory infarct (Fig. 1). MR angiography was normal. He was started on anticoagulation for AF. Within the second day of ICU admission, his consciousness and respiratory status started to recover allowing extubation. Patient’s somnolence improved over the fifth day. He continued to have spatial disorientation and vertical gaze palsy.

Figure 1:

(A) Axial flair image and (B) axial T2-weighted image showing rounded areas of increased signal intensity in paramedian thalami.

PERCHERON ARTERY STROKE: CLINICAL CLUES

Septic patients who developed new-onset AF have a greater risk of in-hospital stroke through hemodynamic collapse, increased systemic inflammation and coagulopathy [1]. Alternatively, new-onset AF may be a potential source of cardio-embolic stroke [1]. Paramedian thalamic strokes account for about 22–35% of all thalamic infarcts [2]. Occlusion of the AOP, which results from cardioembolism, remains an important cause of bilateral paramedian thalamic stroke, with or without rostral midbrain infarction [3]. This artery is a rare anatomical variant where a single thalamic artery arises from the proximal posterior cerebral artery between the basilar artery and the posterior communicating artery and supplies both paramedian territories of the thalami [4].

It is difficult to suspect bithalamic paramedian infarcts because of the complex anatomy, which causes a large clinical variability [3]. AOP infarct usually manifests with the typical triad of ophthalmological signs (65%) (abnormal pupillary reflex and/or vertical gaze palsy), memory impairment (58%) and altered mental status (42%) (hypersomnolence, drowsiness, confusion or coma) [5]. Our patient presented with two out of three typical features of this stroke syndrome, that is, somnolence and vertical gaze palsy. The somnolence and other mental changes have been attributed to interruption of arousal pathways that are relayed from ascending reticular activating system through the thalamus and diffusely to the cortex [5]. Whereas, vertical gaze palsy is likely due to disruption of the cortical input that traverses the thalamus to reach the rostral interstitial medial longitudinal fasciculus [5].

Suspect AOP occlusion in a patient with a decreased conscious level, ophthalmologic signs and cardio-embolic risk factors. Early diagnosis is best obtained with brain MRI with DWI [3]. Treatment of AOP infarction really depends on the pathophysiologic mechanism [4]. Prognosis is subject to the extent of infarction but considered relatively good with regard to mortality and permanent deficits [5].